There are two types of folders for journals: "Public Folders" and "My Folders".
Public Folders can only be created by Game Masters and are available for anyone in the campaign to use for organization. Please note, folders do not affect individual settings on Journal Posts: private journals are still private, and public journals are still public.
My Folders are only usable by yourself for organizing. If you are not a GM, folders you create are automatically put under My Folders. Other players can click into your folders, but will only see posts that are public.
If you need to edit your folders, click the blue "Manage Folders" button in the Folders panel on the right of the main journal page. This page gives you access to sort, edit, or delete your folders. If you delete a folder, any posts inside will remain safe, they will just be removed from the folder.